Tali Sharot on optimism

It is estimated that 80 per cent of the population are optimists. But how do we maintain a positive outlook in the face of reality? At the Wellcome Trust Centre for Neuroimaging, Tali Sharot is teasing apart the neurological basis of optimism. She talks to the Wellcome Trust's Hugh Blackbourn about how a sunny disposition may be the key to our evolutionary success.